Method of using miniature balloon catheter for perfusing

ABSTRACT

This method of using a miniature balloon (102) in blood vessels (104) usually involves using a balloon that is thinner, more delicate (with thickness-controlled walls) than most balloons made previously. The process includes the steps of inserting the balloon (102) into a blood vessel (104) on the end of a cannula (106), inflating the balloon through the cannula until the balloon bursts, and then perfusing perfusate into the blood vessel via the burst balloon (108).

BACKGROUND OF THE INVENTION

This application is a continuation-in-part of application Ser. No.286,100 filed July 22, 1981.

This invention relates generally to the art of miniature ballooncatheters for use in blood vessels, and more particularly, to miniatureblood vessel balloon catheters of a type described in U.S. Pat. Nos.4,085,757 and 4,213,461 (and related applications), to Pevsner and4,029,104 to Kerber. In this respect, the information contained in thosepatents is incorporated herein by reference.

Balloon catheters of the type used in this invention are extremelysmall, since they must fit into very small blood vessels. In thisregard, these balloons have diameters in the range of 0.018-0.033 inch,and are designed to be introduced into a body through 5 French, or lessintroduction catheters.

There are presently, at least two types of miniature blood-vesselballoon catheters with which this invention is concerned, namelydetachable and perfusion. A detachable balloon 12 is depicted in FIG. 1in a blood vessel 10. Basically, the detachable, or pop-off, balloon 12is attached to an elongated, flexible, cannula (sometimes calledcatheter) 14 at a metallic, hollow, pin 16, which is affixed to the endof the cannula 14. The balloon 12, is contracted onto the pin 16 at anenlarged, plug-material, portion 18 having a surrounding compressionband 20.

Briefly, in operation, the balloon 12 is introduced through a 5 Frenchcatheter into a blood vessel using a delivery device, such as the devicedisclosed in U.S. Pat. No. 4,159,022 to Paul H. Pevsner. Using thisdelivery device, the balloon is manipulated to pass through bloodvessels, making turns when necessary, and going into branches wheredesired, by means of "parachute effect", and various othermanipulations. To accomplish this, a surgeon, among other things,inflates and deflates the distal inflatable portion 22 of the balloon 12via the flexible cannula 14 (whose proximal end is outside of the body)and the metallic, hollow, pin 12. When the inflatable portion 22 isinflated it is driven by blood flow with a "parachute effect." In thisrespect, the surgeon must continually inflate and deflate the inflatableportion 22 according to exigencies of the tortuous path he is trying toget the balloon to follow. Once the balloon arrives at its desireddestination, a procedure that is performed with the balloon is toinflate the inflatable portion 22 until its outer surface contacts theinner surface of the vessel 10, as is shown by dashed lines in FIG. 1.The balloon is then further inflated to provide pressure releasing themetallic pin 16 from the plug-material portion 18 and the cannula 14from a shroud portion 24 of the balloon. In addition, in someembodiments there is a hole 26 in the side of the metallic pin 16 which,when pressure within the hollow pin 16 becomes great enough, begins tosignificantly expand the shroud 24, thereby aiding in release of thecannula 14 and the pin 16 by the shroud 24 and the plug-material portion18. Once the cannula 24 and the pin 16 are withdrawn from the balloon12, the plug material 14, in conjunction with a compression band 20,seals the mouth of the inflatable portion 22, thereby leaving theinflatable portion 22 inflated as is shown in dashed lines 22' inFIG. 1. Thus, the inflated balloon is left wedged within the bloodvessel 10, with the walls of the blood vessel 10 bulging out somewhat atthe balloon, as is indicated by dashed lines at 10'.

A perfusion balloon system of FIG. 2 operates substantially the same asthe device of FIG. 1 with regard to the method of transporting theballoon to a position within a blood vessel 10. However, once aperfusion balloon 28 is in a desired position, it is not "popped off" asis the balloon 12 of FIG. 1. Instead, in the prior art, an inflatableportion 30 has a reinforced hole 32 in the tip thereof which issubstantially closed when the balloon is uninflated or inflated to onlya small degree. However, when the balloon is significantly inflated, asis shown by dashed lines 34 in FIG. 2, the perfusion hole 32 opens upand a perfusion liquid is perfused into the blood vessel 10. Thereafter,the balloon is deflated and pulled out of the body, along with thecannula 14 and a metallic pin 36. It should be noted that the metallicpin 36 is different from the metallic pin 16 in that it does not includea hole 26. Further, the balloon system of FIG. 2 differs from theballoon system of FIG. 1 in that the pin 36 is more solidly attached tothe balloon 28, so that the balloon 28 does not detach, or pop-off, asdoes the balloon 12 of FIG. 1.

Although the prior-art method of perfusing is highly beneficial for manyapplications, this invention provides another method of perfusing into ablood vessel with a miniature balloon which is superior for otherapplications.

It will be appreciated by those skilled in the art that the balloons 12and 28 of FIGS. 1 and 2, respectively, must have inflatable portions 22and 30 which easily inflate and deflate when desired for aiding in thedelivery of the balloons to desired locations, while not prematurelybeginning the procedures of the respective balloon systems, namely,detaching the balloon of FIG. 1, or perfusing from the balloon of FIG.2. Further, the inflatable portions 22 and 30, when fully inflated topop off or perfuse, must not rupture blood vessel walls 10 in order toperform these procedures. In other words, the pressure forces must becarefully balanced so that the balloons inflate and deflate fortransportation, inflate completely for performing their main procedures,and perform their main procedures without rupturing blood vessels.

In this regard, when perfusing through the referenced hole 32 of FIG. 2one must be careful not to try to perfuse too fast and thereby riskinflating the balloon to such an extent that it ruptures the bloodvessel. When perfusing with such a method the speed at which one canperfuse through a small hole depends not only on the construction of theballoon but also on the thickness of the perfusate. Thus, it is anobject of this invention to provide a method of perfusing with aminiature balloon which allows one to perfuse faster than previously butin which the danger of rupturing blood vessels is not so great as it waspreviously. However, it is also an object of this invention to providesuch a new method of perfusing which still allows the use of a balloonwhich can be "parachuted" into position in the same manner as previousballoons described above.

In the past, such balloons have been constructed by dipping mandrilswhich are shaped like the balloons into a container, or vat, of liquidsilicone rubber (silicone rubber dissolved in a solvent such as ethylether, Trichlorethylene, phenol or butyl alcohol). The liquid siliconerubber adheres to the mandril, and when the mandril is removed from thevat the silicone rubber cures, or dries. Thereafter, the balloon isremoved from the mandril. Such a silicone rubber solution (liquidsilicone rubber) has been formed of approximately 15% silicone rubberand 85% solvent. Normally the mandril need only be dipped into thesolution once. Such a prior art system of making balloon catheters isfully described in U.S. Pat. No. 4,213,461 to Paul H. Pevsner.

A problem with balloons constructed by dipping a mandril into a vat ofsilicone rubber solution is that the walls of the balloon are relativelythick, thereby making the balloons too large to go into many smallervessels and also requiring excessive pressure to inflate the balloons toperform desired functions therewith. That is, the balloons rupture wallsof smaller vessels prior to performing their functions. Anotherdifficulty with unduly thick walls is that the balloons cannot navigatetortuous turns in small vessels of the head, pelvis and bowels.

This application describes a method of making balloons for miniatureballoon catheters which have thinner, and more delicate, walls than thewalls of prior-art balloon catheters. By using this new method thethickness of balloon walls can be controlled to a greater degree thanwas previously possible.

SUMMARY

According to principles of this invention balloon catheters constructedto have thin, thickness-controlled, walls are "parachuted" into positionin blood vessels. Thereafter, the balloons are inflated via an attachedcannula until they burst. A perfusate is then inserted via the cannulainto the blood vessel through the burst balloon.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages will beapparent from the following more particular description of a preferredembodiment of the invention, as illustrated in the accompanying drawingsin which reference characters refer to the same parts throughout thedifferent views. The drawings are not necessarily to scale, emphasisbeing placed upon illustrating principles of the invention in aparticular manner.

FIGS. 1 and 2 are side-sectional views depicting prior-art ballooncatheters of a type with which this invention is concerned, mounted oncannulas and pins in blood vessels, FIG. 1 depicting a pop-off balloon,and FIG. 2 depicting a perfusion balloon;

FIG. 3 is a side view of a mandril for making a pop-off balloonaccording to principles employed in making a perfusion balloon used inthe method of this invention;

FIG. 4 is a side view of a mandril for making a perfusion balloon usedin the method of this invention;

FIG. 5 is a close-up side view, shown partially in section, of the tipof the mandril of FIG. 4 having silicone rubber coated thereon;

FIG. 6 is a side view, shown partially in section and partially inschematic, of spraying apparatus for making balloons used in the methodof this invention;

FIG. 7 is a view taken on lines 7--7 of FIG. 6; and

FIGS. 8 and 9 are side cutaway views of a balloon catheter in a bloodvessel being used to perform the method of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 6, an aerosol sprayer 40 is being used to sprayliquified silicone (a silicone solution comprising approximately 5%silicone rubber and 95% solvent) 42 onto a mandril 44 which is mountedon a cork block 46. With regard to the mandril 44, and the block 46,enlarged views thereof are depicted in FIGS. 3 and 4, with FIG. 3depicting a mandril 48 for making pop-off type balloons of FIG. 1 andFIG. 4 depicting a mandril 50 for making perfusion balloons of FIG. 2.

The aerosol sprayer 40 includes a container 52 and a removable top 54which can be removed for filling the container 52 with silicone solution42. The removable top 54 includes an air-inlet passage 56, an exhaustpassage 58, and an outlet passage 60. The outlet passage 60 communicateswith a dip tube 62, which extends downwardly into the silicone solution42. The container 52 and the removable top 54 are about 2 inches tall.The shell of such an aerosol sprayer is described and sold in theAmerican V. Mueller Catalog, No. 80, Page 739, and is identified thereinas Devilbiss Syringe 177. However, the Devilbiss Syringe 177 used forthis invention is modified in that a plate 64 is soldered at the mouthof its outlet passage 60. The plate 64 includes female threads 66 intowhich male threads of an aluminum, one centimeter, outer-diameter, tube68 is screwed. It should be noted that the outer end 70 of the tube 68is beveled inwardly culminating at a hole 72 which is 1.5 mm across whenfully opened. The plate 64 also has mounted thereon a female-threadedsocket 74 into which a 2-2.5 mm needle 76 is screwed. The needle 76 hasa tip 78 which is beveled at approximately a 30° angle, approximatelythe same as the bevel of outer end 70 of the tube 68, and is positionedto be in the opening 72 of the tube 68. The pointed tip 78, incombination with the hole 72 causes pressurized fluid to be aerosolizedwhen it is forced through the hole 72. Axial adjustment of the pin 76relative to the hole 72 is made by removing the tube 68 from the femalethreads 66, and rotating the needle 76 to cause movement due to threads74. Thereafter, the tube 68 is again screwed into the threads 66. FromFIG. 6 it can be seen that the plate 64 has numerous holes 80 therein toallow silicone solution 42 flowing through the dip tube 62 and theoutlet passage 60 to pass into the tube 68 around the needle 76.

The container 52 is pressurized in a space 82 above the siliconesolution 42 through the air-inlet passage 56 which communicates with apressurized air, or oxygen, source 84 via a pressure regulator 86. Apressure gauge 88 enables an operator to know what pressure is beingapplied to the space 82. With regard to this pressure, pressure sourcesare available in hospitals ranging from 100-1,000 psi, however, thepressure applied to the space 82 in the aerosol sprayer 40 should beless than 25 psi. Thus, the pressure regulator 86 must be sized inaccordance with the pressurized air source 84.

Once pressurized air, or oxygen, is being applied through the air-inletpassage 56, the space 82 will be pressurized if the exhaust passage 58is covered, however, it will not be significantly pressurized if theexhaust passage 58 is not covered. Thus, the exhaust passage 58 acts asan on/off switch which can be actuated by an operator covering it, ornot covering it, with his finger.

In making perfusion balloons used in the method of this invention, aswell as in making other beneficial balloons, one mixes a siliconesolution 42 having a concentration of silicone to solvent 42 of lessthan 15%, preferably around 5%, and puts this in the aerosol sprayer 40by removing the container 52 from the removable top 54. Once thecontainer 52 is again screwed onto the removable top 54, pressure fromthe pressurized air source 84 is applied through the pressure regulator86 to the space 82 via the air-inlet passage 56, this pressure beingsomething less than 25 psi, preferably between 15 and 25 psi. Theoperator adjusts the relative positions of the tube 68 and the needlevalve 76, testing the mechanism by placing his finger over the exhaustpassage 58. If liquid silicone is not aerosolized when it is ejectedfrom the hole 72, the operator must remove his finger from the exhaustpassage 58 and readjust the relative positions of the tube 68 and theneedle valve 76. This procedure is repeated until operation of thedevice aerosolizes the silicone solution.

Now the operator aims the aerosolized silicone solution at the mandril44, which is stationarily mounted on a cork block 46, to thereby applythe aerosolized silicone solution to the mandril, manipulating theaerosol sprayer 40 about the mandril 44. The operator can cause abuildup 90 of silicone solution at various points on the mandril as hedesires. For example, with reference to FIG. 5, the operator can cause abuildup 90 of silicone about a needle 92 which molds a perfusion hole 94in a balloon 96 being made. This buildup 90 reinforces the perfusionhole 94, which is desirable as is fully described in U.S. Pat. No.4,213,461 to Paul H. Pevsner. Similarly, a buildup can be caused at anindentation 98 (FIG. 3) in the mandril 48 to create plug materialcorresponding to the plug material 18 of FIG. 1.

So much solution is thusly applied to the mandril 44 to create a thin,approximately-uniform, coat of silicone solution, with the exception ofthose areas where the operator has tried to create a buildup. The coatcan be virtually as thin as the operator desires, and certainly shouldnot be sufficiently thick to cause "runs" of drops down the mandril. Ifthe operator desires to have a thicker (although thinner than mostdipped balloons) balloon, he allows the first coat of silicone solutionto cure (air cure from 24-48 hours, oven cure at 130°-140° F. for around1/2 hour), and then he applies a second coat. An average balloonrequires approximately three coats of silicone solution and even so thiscomposite coat is thinner and more delicate than a normal coat which iscreated by dipping a mandril in silicone solution once. An operator cancontrol balloon wall thickness by controlling the number of coats.

An embellishment of this method is to apply a positive terminal of anelectrical source 100 to the mandril 44 and its negative terminal to theaerosol sprayer 40. Thus, aerosol mist particles have negative chargeswhich are attracted to the positive charge of the mandril. In thisrespect, it has been learned that even if the aerosol sprayer, and theparticles emitted therefrom, are not energized by an electrical source,the mist particles are normally negatively charged. Therefore, it isreally only necessary to positively charge, or ground, the mandril 44 inorder to get attraction. However, for completeness sake, an electricalsource 100 is shown in FIG. 6 which may be necessary under differentconditions than those which existed for tests which have been run todate. It should be noted that this invention works quite well evenwithout employing an electrical source.

It has been found from tests that minute particles of metal, such astitanium, barium, tantalum, bismuth, and silver can be mixed in thesilicone solution 42 and sprayed with the aerosol sprayer 40. Suchparticles, are also aerosolized and are uniformly spread on the mandril44. When thusly used, the container 52 is shaken to keep the minutemetallic particles uniformly distributed within the silicone solution 42prior to spraying.

Yet a further embellishment of this method is to cover the mandrils 44,48 and 50 with a coat of Teflon and then to roughen this coat of Teflonwith very fine sandpaper, or the like. The purpose of the "roughening"is to make it easier for the aerosolized particles to adhere to themandril. This could be accomplished simply by roughening the surface ofa metal mandril 44, however, when this is done it is somewhat difficultto remove the balloon from the mandril. Thus, Teflon is applied, and theTeflon is roughened. With regard to removing balloons from the mandril,this can be accomplished by dilating the balloons with a solvent, suchas ethyl ether.

It will be understood by those skilled in the art that the methodproduces thinner and more delicate miniature balloon catheters than didthe prior-art "dipping" method. In addition, this method allows one tomake uniform, radio-opaque miniature balloon catheters which aresuperior to those which could be made in the prior art.

When balloons are made with this method, they can be made sufficientlythin that the balloons can be inflated and exploded before the walls ofthe balloon even contact the walls of blood vessels, which therebyallows one to use the inflation/deflation aspect of the balloon to helptransport it to a proper position using "parachute effect" andthereafter enables the operator to explode the balloon by overinflatingit, without risking damage to the vessel.

In this respect, the method of practicing this invention is depicted inFIGS. 8 and 9. In practicing the method of this invention, a perfusionballoon 102 having no perfusion hole therein, but being constructed tobe extremely thin in accordance with the spraying method describedabove, is introduced into a blood vessel 104 and guided to anappropriate position within the blood vessel 104 by inflating anddeflating the balloon 102 via a cannula 106. Once the balloon 102 is inan appropriate position, it is inflated further via cannula 106 until itbursts. In the preferred embodiment, the balloon is designed to lightlytouch the walls of the blood vessel 104 before it bursts in order toprovide a greater margin for inflating and deflating the balloon 102during positioning, however, in some embodiments, the balloon isdesigned to burst before it wedges itself in the blood vessel 104 inorder to provide a greater safety margin for protecting the blood vesselagainst being ruptured. In any event, once the balloon 102 has burst itbecomes a deflated balloon 108 having a rather large rupture hole, orholes, 110 therein. At this point, a perfusate is introduced into thecannula 106 from outside the body and this perfusate is forced throughthe cannula 106 and the balloon 108 into the blood vessel 104 via therupture hole, or holes, 110.

Still further, balloons can be made sufficiently thin and delicate withthe method described herein so that the releasability at desiredpressures can be chosen to a finer degree, not previously possible undera prior-art "dipping" technique for making balloons.

Balloons made with the method described herein have been introducedeasily through 4 French catheters, which was not practical with dippedballoons. Further, balloons made with this method have been transportedinto smaller vessels than was previously possible with dipped balloons.In addition, it is noted that about six sprayed coats according to themethod of this invention is equal to one dipped coat according to theprior art. However, even where a sufficient number of coats is sprayedonto a mandril to create a balloon of the thickness of a dipped balloon,the sprayed balloon is superior in that it is more flexible. Thisphenomenon is not understood by the inventor. It is noted that prior-artdipping is done in a 15% solution because when the solution is thinneran insufficient amount sticks to the mandril.

While the invention has been particularly shown and described withreference to preferred embodiments, it will be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention.

It is noted that much of the apparatus described herein is of a researchnature because applicant has not progressed beyond this point in thedevelopment of this invention.

The embodiments of the invention in which an exclusive property orprivilege are claimed are defined as follows:
 1. A diagnostic andtherapeutic method for carrying out perfusion procedures in smallvessels comprising the steps of:preparing a miniature balloon catheterassembly including an inflatable balloon formed to be extremely thin byaerosolizing balloon-catheter-material solution onto a mandril andallowing it to cure, said balloon having no perfusion hole therein andbeing connected to a distal end of a resilient cannula, said balloon andsaid cannula having a size for insertion into blood vessels and saidinflatable balloon being constructed to be inflated and deflated in saidblood vessels for being transported and directed therein by the flow ofblood, said balloon being further constructed to be inflated untilbursting in a particular blood vessel without damaging said particularblood vessel; inserting the distal end of said cannula including saidinflatable balloon, into a blood vessel; attaching the proximal end ofsaid cannula to a source of pressurized fluid and pressurizing theballoon to partially inflate the balloon to permit the balloon and theattached cannula to be transported by blood flow within the vessel tosaid particular blood vessel; increasing the fluid pressure inside theballoon portion to expand the thin balloon portion until said balloonportion bursts, thereby causing a rupture hole in the thin balloon; andinserting a therapeutic perfusate into the proximal end of said cannulaand perfusing said perfusate into said blood vessel via said rupturedhole in said burst balloon.
 2. A method as in claim 1 wherein saidballoon is made by the steps of: aerosolizing a first coat of saidballoon-catheter material solution onto said mandril; allowing saidfirst coat to cure; thereafter aerosolizing at least one additional coatof said balloon-catheter material solution onto said cured coat;thereafter allowing said additional coat to cure, the number of coatsbeing chosen to provide a particular bursting pressure; and thenremoving from said mandril said first cured coat and said additionalcured coat as a unit forming said miniature balloon.
 3. A method as inclaims 1 or 2 wherein said balloon-catheter-material solution is arubber solution mixed in proportions of less than 15 percent rubber tosolvent.
 4. A method as in claim 3 wherein said proportion of rubber isaround 5 percent.
 5. A method as in claim 3 wherein said rubber issilicone.
 6. A method as in claim 1 wherein saidballoon-catheter-material solution is sprayed with an aerosol apparatusthrough an opening whose effective area is controlled by a needle valve.